446 research outputs found
Structure of Higher Spin Gauge Interactions
In a previous paper, higher spin gauge field theory was formulated in an
abstract way, essentially only keeping enough machinery to discuss "gauge
invariance" of an "action". The approach could be thought of as providing an
interface (or syntax) towards an implementation (or semantics) yet to be
constructed. The structure then revealed turns out to be that of a strongly
homotopy Lie algebra.
In the present paper, the framework will be connected to more conventional
field theoretic concepts. The Fock complex vertex operator implementation of
the interactions in the BRST-BV formulation of the theory will be elaborated.
The relation between the vertex order expansion and homological perturbation
theory will be clarified. A formal non-obstruction argument is reviewed. The
syntactically derived sh-Lie algebra structure is semantically mapped to the
Fock complex implementation and it is shown that the recursive equations
governing the higher order vertices are reproduced.
Global symmetries and subsidiary conditions are discussed and as a result the
tracelessness constraints are discarded. Thus all equations needed to compute
the vertices to any order are collected. The framework is general enough to
encompass all possible interaction terms.
Finally, the abstract framework itself will be strengthened by showing that
it can be naturally phrased in terms of the theory of categories.Comment: A few changes and additions made in the Introduction. Three
references added. Typos corrected. Text agrees with published version in J.
Math. Phys. except for minor journal specific proof-reading changes. 61 page
Microscale distribution patterns of terrestrial bryophytes in a subalpine forest: the use of logistic regression as an interpretive tool
This study investigated microhabitat relationships of terrestrial bryophytes in a subalpine forest of coastal British Columbia. Substratum affinities were characterized for dominant bryophytes. Logistic regression analysis was used to gain insight into the ecological determinants of fine scale (0.1 m2) bryophyte distribution by examining the predictive relationship between bryophyte species occurrence and localized environmental conditions, as well as the coverage of other bryophytes. The predictive relationships were compared to evaluate the relative importance of environmental factors versus interspecific interactions in structuring bryophyte communities. The results indicate that bryophytes show unique responses in their relationships to environmental conditions and other bryophytes. Positive feedback appears to be an important process among terrestrial bryophytes in subalpine forests
Simple sequence repeats in Neurospora crassa: distribution, polymorphism and evolutionary inference
<p>Abstract</p> <p>Background</p> <p>Simple sequence repeats (SSRs) have been successfully used for various genetic and evolutionary studies in eukaryotic systems. The eukaryotic model organism <it>Neurospora crassa </it>is an excellent system to study evolution and biological function of SSRs.</p> <p>Results</p> <p>We identified and characterized 2749 SSRs of 963 SSR types in the genome of <it>N. crassa</it>. The distribution of tri-nucleotide (nt) SSRs, the most common SSRs in <it>N. crassa</it>, was significantly biased in exons. We further characterized the distribution of 19 abundant SSR types (AST), which account for 71% of total SSRs in the <it>N. crassa </it>genome, using a Poisson log-linear model. We also characterized the size variation of SSRs among natural accessions using Polymorphic Index Content (PIC) and ANOVA analyses and found that there are genome-wide, chromosome-dependent and local-specific variations. Using polymorphic SSRs, we have built linkage maps from three line-cross populations.</p> <p>Conclusion</p> <p>Taking our computational, statistical and experimental data together, we conclude that 1) the distributions of the SSRs in the sequenced N. crassa genome differ systematically between chromosomes as well as between SSR types, 2) the size variation of tri-nt SSRs in exons might be an important mechanism in generating functional variation of proteins in <it>N. crassa</it>, 3) there are different levels of evolutionary forces in variation of amino acid repeats, and 4) SSRs are stable molecular markers for genetic studies in <it>N. crassa</it>.</p
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